Marked card readers are well known in the art for use with lottery documents, multiple transaction documents, standardized test forms and the like. These marked card readers are used in conjunction with a substrate of the type having a plurality of data entry regions which are darkened by a pencil thereby making the data entry regions contrast with the areas of the substrate surrounding the data entry regions. The substrate is then placed in data communication with an optical sensing device associated with the reader. A typical prior art marked card reader is disclosed in U.S. Pat. No. 4,578,569 to Arp et al. Disclosed therein is a hand-fed data-card reader compatible with cards of different widths and having a selectively actuable perforator for conveying a card past a reader head and for selectively canceling a desired card by the perforation thereof. Cards are conveyed via a belt/pulley drive train that is operably coupled to a spiked perforate that engages each card at one of two pressures so as to selectively convey the card with or without embossing the surface. More recently, progress has been made with increasing the accuracy of reading information from the substrate.
U.S. Pat. No. 5,711,673 to Grundy, Jr. discloses a method for interpreting a plurality of response marks on a scannable surface that includes an adjustable read level threshold. The adjustable read level threshold enables distinguishing between marks intended to be present on the substrate from marks not intended to be placed on the substrate. A drawback with prior art card reading systems, however, is that the same are expensive to implement.
What is needed, therefore, is a low cost marked card reader which is capable of accurately interpreting information on a substrate.